Double break high voltage disconnect switch

ABSTRACT

High voltage disconnect switchgear having a double break contact operation. The main movable contacts are slidably mounted radially within a rotating insulating carrier. The opening operation first withdraws the main movable contacts into the carrier and then rotates the carrier thereby providing both the double break and the insulating interposition of the carrier between the main movable contacts and the stationary contacts. The main contacts are protected by arcing contacts which make first on closing and break last on opening. The arcing contacts are carried by the rotatable carrier and operate in an arcuately shaped arc chute adjacent the carrier.

United States Patent 11 Netzel [451 Aug. 20, 1974 DOUBLE BREAK HIGH VOLTAGE DISCONNECT SWITCH [75] Inventor: Philip C. Netzel, Milmont Park, Pa.

[73] Assignee: l-T-E Imperial Corporation, Spring House, Pa.

22 Filed: Sept. 13, 1973 [2]] Appl. No.: 396,757

Primary Examiner-Herman J. Hohauser Attorney, Agent, or Firm-OstrOlenk, Faber, Gerb & Soffen [5 7 ABSTRACT High voltage disconnect switchgear having a double break contact operation. The main movable contacts are slidably mounted radially within a rotating insulating carrier. The opening operation first withdraws the main movable contacts into the carrier and then rotates the carrier thereby providing both the double break and the insulating interposition of the carrier between the main movable contacts and the stationary contacts. The main contacts are protected by arcing contacts which make first on closing and break last on opening. The arcing contacts are carried by the rotatable carrier and operate in an arcuately shaped arc chute adjacent the carrier.

PAIENIEDumzOwn I 3 3 sum 10; 9

PAIENIEDwczown I 3.830.994

Disconnect switches used at lower voltages are generally knife blade switches with a single contact gap. The use of a switch of this type at high voltage such as 38 kV would require a considerable amount of space because of the large clearances needed to maintain dielectric strength in the installation.

A primary object of the present invention therefore is to reduce the voltage stress in the open contact gap by providing a disconnect load break switch with a double contact break and in addition providing a means for FIG. 14 is a side view partly in section of the load break disconnect switch of FIGS. 11 and 12.

FIG. 15 is an enlarged view of the operating mechanism shown in FIGS. 8, 11 and 12.

FIGS. 16 and 17 are diagrammatic views illustrating the operation of the opening and closing mechanism.

Referring now to FIG. I, the movable contact structure 20 there shown is supported by and driven by the shaft 21. A double ended crank 22 is fixed to the shaft 21 and rotatable, therewith; ()ne end of crank 22 is connected by pin 24 to the link 25 which, in turn, is connected by pin 26 to the movable contact member or rod 27; similarly the end of crank 22 is connected by pin 30 to link 31 which, in turn, is connected by pin 32 to the movable contact or rod 33. The movable contact structures 27 and 33 are contact rods having respecinterposing insulating material between the contacts when the contacts are open.

A further object of the present invention is the provision of a simplified arcing contact structure and arc extinguishing means.

The foregoing and many other objects of the present invention will be described in connection 'with the following description and drawings in which:

FIG. 1 is a schematic view of the novel load disconnect double break contact switch of the present invention in the closed or connected position.

FIG. 2 is a view corresponding to that of FIG. 1 showing an intermediate stage in the operationof the load break disconnect switch from the closed circuit position of FIG. 1 to the open circuit position of FIG. 3.

FIG. 3 is a view corresponding to those of FIGS. 1 and 2 showing the full open or disconnect condition of the load break disconnect switch.

FIG. 4 is a schematic view corresponding to FIG. 1 showing a somewhat modified structure of the operating mechanism for the load break disconnect switch.

FIG. 5 is a vertical cross-sectional view of an actual embodiment of the novel load break disconnect switch schematically shown in FIGS. 1, 2 and 3.

FIG. 6 is a view partly in cross-section taken from lines 6-6 of FIGS looking in the direction of the arrows. It is also a view taken from lines 6-6 of FIG. 7. FIG. 7 is a side view of the novel load break disconnect switch of FIGS. 1 to 3,5 and 6 showing the movable contact members in the closed position.

FIG. 8 is an enlarged view of the operating mechanism for the load break disconnect-switch shown in FIG. 5.

FIG. 9 is an enlarged view of the load break disconnect switch showing particularly the arcing contact structure.

FIG. 10 is a view taken on line 10-10 of. FIG. 9

tively contact tips 34 and 35. Contact rods ride in the diametrically arranged recesses 37 (for contact rod 33) and 38 (for contact rod 34) in the disc 40 which is constructed of insulating material.

The recesses 37 and 38 communicaterespectively with the larger internal recesses 42 and 43 within the disc 40. Compression springs 45 (for contact rod 33) and 46 (for contact rod 27) are captured between the respective outer walls 50, 51 of the larger recesses 42, 43 and the spring keepers 47, 48 on the respective contact rods 33 and 27 in order to bias the contact rods 33 and 27 to theietracted position shown in FIGS. 2 and 3. The'position however which is shown for the shaft 21 in FIG. 1 andthe links 25-and 31 is such that the crank 22, shaft 21, the links 31 and 35 overcome the force of the respective springs45 and 46 to drive the contact tips '34, 35 of the movable contact rod 27 and 33 into engagement with the stationary contact tulips 52, 53 which are mounted on the stationary contact supports 54 and 55. l

When the disconnect contact is to be opened, the shaft 21 is turned clockwise with respect to FIG. 1. The initial movement of the shaft 21 clockwise with respect to FIG. 1 results in a pulling inward of each of the contact rods from the position of FIG. 1 to the position of FIG. 2, as therein shown. On completion of this inner movement of the contact rods 27 and 33 with the contact tips now flush with the outer surface 60 of the disc 40-, the ends of the crank 22 engage the surfaces 61 and 62 respectively within the disc 40, continued rotation of the shaft 21 in a clockwise direction now rotates the disc to the position shown in FIG. 3 where the movable contact tips'35 and 34"are displaced a full from the stationary contact tulips 53 and 52. 5

Thus it will be seen that the rotation of the shaft 21 through approximately .l2O in a clockwise direction results in an opening of the disconnect contacts. The first 30 ofv rotation produces the operation of withdrawing the movable contact rods 27 and 33'frorn their respective stationary contacts to the position of FIG. 2. The remainder of the rotationof the shaft 21', through the remaining 90, positions the contacts at the full double break open position shown in FIG. 3,

The compression springs 45 and 46, as' shown, serve to bias the moving contact rods 27 and 33 toward the open position. These springs are fully compressed in the closed position shown in FIG. 1.

In the reverse operation, when the disconnect contact double break switch is in, the position shown in FIG. 3, rotation of shaft 21 in a counterclockwise direction will first result in the rotation of the disc 40 from the position of FIG. 3 to the position of FIG. 2 where the stop 70 has moved from the position of FIG. 3 to the position of FIG. 2, halting further rotation of the disc 40 at the position where the movable contacts are aligned with the stationary contacts; further rotation of the shaft 21 will result in movement of the movable contact rods 27 and 33 into engagement with the stationary contacts as shown in FIG. 1.

It will be noted that the stop 70 fixes the closed position of the disc in FIGS. 1 and 2 where the movable contacts may be operated into engagement with the stationary contacts and the stop 70 also fixes the open position of the disc 40 and hence of the shaft 21.

The compression springs 45 and 46 which hold the contacts in withdrawn-position in the position of FIG. 3 also ensure that the disc 40 will first be rotated by the rotation of shaft 21 when the structure is moved from the position of FIG. 3 to the position of FIG. 2, constituting a sufficient connection between the shaft 21 and the disc 40 so that the contacts tips 34 and 35 will not be moved out during this rotation from the position of FIG. 3 to the position of FIG. 2 until the stop 70 is engaged as shown in FIG. 2 whereupon further rotation of shaft 21 in a counterclockwise direction will result in the movement of the contacts into engagement as shown in FIG. 1.

In FIG. 4 there is shown a modified'form of the structure wherein all elements are the same except that the crank 22a is provided with cam surfaces which engage with discs 73 formed at each end of the contact rods 33 and 27, so that the structure functions in the-same way as with the link construction described in FIGS. 1, 2 and 3.

It should also be noted here that in addition to mounting the movable contacts in the disc 40 of insulating material, a solid insulating shield 80 is provided for the stationary contact on each side, the said shield of insulating material having a recess 81 on each side into which the respective stationary contact structures 54, 55 project. The solid insulating shield 80 is provided with and supports are extinguishing means'operating in connection with arcing contacts as hereinafter described.

It will thus be seen that by the means shown schematically in FIGS. 1, 2 and 3, as well as the modified form of FIG. 4, a double break disconnect switch is formed which in addition to the double break permitting higher voltage gradients, the insulating disc 60 coacting with the insulating member 80 provides additional interposition means with respect to the disconnect contact providing in effect an increased break.

One of the essential elements of the operation of a disconnect switch of the form here shown is that its operation be continuous and rapid, particularly from the closed position of FIG. 1 to the open position of FIG. 3. Hence means must be provided so that the operation from the FIG. 1 position to the FIG. 2 position and then to the FIG. 3 position will be continuous and withouta break in movement so that any are which is drawn between the movable and stationary contacts will be quickly extinguished by the lengthening of the are as the contacts are moved from the position of FIG. 2 to the position of FIG. 3.

Therefore, a direct manual. or other mechanical oper-- ation should not be used'in connection with this type of double break switch; since the operation should be continuous and rapid, it is preferred that a charged spring be used in order to effect this operation. It is also desirable, although not as essential, that the switch be closed rapidly and by continuous movement. Therefore, the preferred method of operating the shaft 21 is through an overcenter spring arrangement which, in effect, will provide a charged spring for operation in either direction and thereby ensure a smooth continuous and rapid operation so that any are which may be drawn will not hang in the position of FIG. 2 but will be rapidly extinguished by the continuity of movement from the position of FIG. 1 through the position of FIG. 2 to the position of FIG. 3.

An actual structure embodying the concepts herein described in connection with the schematic views of FIGS. 1, 2 and 3 is set forth in detail in connection with FIGS. 5 to 15.

Referring first to FIG. 5 where a single pole double break disconnect switch is shown, the shaft 21, located within the disc 40, has the same operation as that previously described in connection with FIGS. 1, 2 and 3. Back connection stud 101 is connected by the strap 102 to the upper stationary contact structure in the area-55; the'lower back connection stud 104 is connected by the strap 105 to the lower stationary contact structure in the area 54.

The shaft 21 is operated by a crank connected by pin 111 to the link 112. Link 112 is at its other end connected by the pin 113 to the crank 114.

Crank 114 is a bell crank type of link which is loosely rotatably mounted on the shaft 115. The'opposite pin 116 of the bell crank 114 is connected to toggle link 117 which'through the toggle pin 118 is connected to toggle link 119, the opposite end of which is connected and rotatably mounted on the stationary pin 120. The connecting link 112 is an adjustable link which may be adjusted in length by the screw adjustment located adjacent the end 122 thereof. A tension-spring-carrying rotatable member is also rotatably mounted around shaft 115. j

A tension spring 131 is connected between the pin 132 at the outer end 133 of the spring-carryingmember 130 and the toggle pin 118 of the toggle As will be seen from the dotted line showing of FIG. 5 and the diagrammatic showing of FIGS. 16 and 17, when the spring carrying link 131 is moved from the dotted line position of FIG. 5 and the position shown diagrammatically in FIG. 16 to the dotted line position of FIG. Sand the position shown diagrammatically in FIG. 17, the tension spring 130 is moved from the solid line position of FIG. 5 and the diagrammatic position of FIG. 16 (where it urges the toggle 117-119 to extended position)'to an overcenter condition above the toggle pin 118 (where the tension spring 130 collapses the toggle 117-119) thereby causing bell crank 114 to rotate in acounterclockwise direction. This results in pulling down the link 112, thereby turning the shaft 21 in a clockwise direction and rotating the disc 40 clockwise from the position schematically shown in FIG. 1 through the position schematically shown in FIG. 2 to the full open position schematically shown in FIG. 3.

The means for moving the tension spring carrier 130 from the solid line position of FIG. 5 and the diagrammatic position of FIG. 16 to the dotted line position of FIG. 5 and the diagrammatic position of FIG. 17 includes the crank which is secured-to the shaft '1 15 for rotation therewith.

The crank 140 is provided with the extensions 141 and 142. In the closed position of the switch, the bearing pin 144 extending from the side of the tension spring carrier 130 is against the extension 141 of crank 140. When the shaft 115 is rotated in a counterclockwise direction, the crank 140 is lifted, thereby raising the pin 144 of the tension spring carrier 130 and thereby raising thespring carrier 130 to the dotted line position 130a from the solid line position of FIG. 5 and the diagrammatic position of FIG. 16.

As the spring carrier 130 passes the position where the spring 131 begins to move above the line between the pin 120 at the end of toggle link 119 and the toggle pin 118, the tension spring now begins to pull up on the toggle pin 118 and the spring carrier 130 snaps to the dotted line position 1301) and the diagrammatic position of FIG. 17, collapsing the toggle 117-119 and moving the link 112-122 .to the lower dotted line position of FIG. 5.

This results in rotation of crank 110 in-a clockwise direction, thereby rotating the contact carrying shaft 21 in a clockwise direction, similarly rotatingthe disc 40 and performing the operation of movement of the contacts from the position of FIG. 1 through the position of FIG. 2 to the full open position of FIG. 3.

Similarly, when the shaft 1 is rotated in an opposite direction, that is in a clockwise direction with respect to FIG. 5, the crank 140 which is now in the upper position moves clockwise or downwardly so that the extension 142-engages the pin 144 of the tension spring carrier 130; when the line of the ,axis of the spring 131 passes below the axis from pin 120 to toggle pin 118, the toggle is snapped to the extended position shown in the solid lines of FIG. 5 and the diagrammatic sketch of FIG. 16 to rotate the crank 114 in a clockwise direction and raise the link 112-122 to rotate the contact carrying disc 40 from the position schematically shown in FIG. 3 through the position schematically shown in FIG. 2 to the closed circuit position of FIG. 1.

In FIG. 5 the structure is shown at the initiation of the operation from the closed to the open position, that is the crank 140 has been rotated so that the extension 141 engages the pin 144. In the at rest position, the crank 140 should normally have moved to a position where the extension 141 is just below thepin 144. The position of the tension spring carrier 130 is fixed by stops 150 at the top and 151 at the bottom which may engage pin 132 to which one end of the tension spring 131 is connected, or to an external pin at that location. It will be seen that in rotation of the crank 140 in a counterclockwise or upward direction with respect to FIG. 5 that the upper extension 142 of the crank will move out of the way and beyond the line of engagement of the tension spring carrier pin 132 with the upper stop 150 to permit the snap action to occur. The spacing between the extensions 141, 142 is chosen to permit this action to occur. (See also FIGS. 8 and 9).

It will also be seen that in FIGS. 8 and 9 the solid line position shown for the tension spring carrier and the various parts is the closed circuit position corresponding to that shown in FIG. 5,,and the dotted line positions correspond to the dotted line positions of FIG. 5

gear 142 on the shaft 115. Therefore rotation of the shaft in one direction will result in the snap action operation of the switch from the closed to the open position under the influence of the spring 131 and rotation of the shaft 160 in the opposite direction will result in a similar snap action operation of the switch from the dotted line or open position of FIGS- 5 and 8 (shown diagrammatically also in FIG. .17) to the solid line position or closed circuit position of FIGS. 5 and 8 and the position shown diagrammatically in FIG. 16.

The physical structure of the disc 40 already described in connection with the schematic structure shown in FIGS. 1 2 and 3 is shown in FIGS. 6 and 7. All of the elements shown in the FIGS. 1, 2 and 3 appear in the structure shown in FIGS. 6 and.7 and are therefore similarly numbered. Added structures shown include the extension of the pins 32 for the upper movable contact 33 and the pins 26 for the lower movable contact 27 to provide bearings 201 which ride in the slots 202, 202 in the recess 42 and 43.

As indicated in FIGS. 5 and 8, the entire switch structure is mounted on a base frame 210 having a front support frame 211 and a door 212. The door 212 is provided with an appropriate opening indicated generally at 213 through whichaccess can be obtained for a crank to be connected to or inserted in the shaft 160, the shaft 160 being provided with appropriate recess such as a square or hex recess to receive the crank (not shown). An outer door 214 is provided which maybe locked if desired in order to prevent unauthorized access to the operating members. The lower portion of the switch frame 210 carries a bottom pan 220 to which is secured an appropriate frame 221 for the operating mechanism including the toggle 117-119 and its associated operating elements. The bottom section 210 of the frame also as seen in FIG. 5 carries additional vertical frame and support structures 220, 225, the rear support structure 226, the front support structure and the cross bars or pieces 227, which actually support the switch structure, particularly tee operating shaft 21 and the disc 40 and provide appropriate support for the stationary contacts.

The said support for the stationary contacts includes an appropriately insulated vertical support 230 carried by the cross piece 227 and an additional stand-off insulator or support 231 for the lower stationary contacts and the connection lead 105. Appropriate insulation is provided on the cross piece of the frame 227 as needed.

Arcing contact construction is provided as shown in FIGS. 5, 9, 10 and 12. As seen particularly in FIGS. 10 and 12, a stationary arcing contact support strap 240 is provided at the terminal block 241 at the end of the back connection strap 102 supported by the back connector 101 to which the stationary contact structure 55 is connected. The strap 240 supports a stationary arcing contact 242 which comprises the spring fingers 243, 244 which are held in appropriate relation to each other by the cross connecting member 245 which member may be adjustable in length in order to create appropriate contact pressure. The spring fingers 243, 244 are provided with arcing contact tips 246, 247. The disc 40, as seen in FIG. 12, carries movable arcing contacts 250, 251 which will enter into and cooperate with the stationary arcing contacts 242 when the switch is in the closed position (FIG. 5). The movable arcing contact 250 shown in FIG. 10 and at the top of the disc in FIG. 12 is duplicated exactly by the movable arcing contact 251 in FIG. 12 at the bottom. A similar stationary arcing contact to that shown in FIG. is provided at the bottom connected electrically and supported by support structure for the stationary contact 54. The movable arcing contact in each case is electrically connected to the movable contact rod 33 and rod 27 through the shaft 21. I

An arc extinguisher (see FIGS. 10 and 12) is provided by a pair of plates 253, 254 which are arcuately shaped and appropriately supported in stationary position at the terminals.

It will be noted that the main contacts disconnect by the initial 30 operation of the'shaft 21 as shown in the initial disconnect operation when the switched structure is moved from the position of FIG. 1 to the position of FIG. 2. At this time, the arcing contacts of FIGS. 10 and 12 remain in position because the disc 40 has not moved. When the disc 40 is, on a continuation of the movement of the shaft 21, moved from the position of FIG. 2 to the position of FIG. 3, then the movable arcing contacts 250 separate from the stationary arcing contacts 242 and travel in the channel defined by the plates 253 and 254. The are is then drawn between the arcuately shaped plates 253 and 254.

The arc extinguishing plates between which the arc is drawn are preferably made of glass-tilled melamine or similar material which will gassify when in contact with the arc. The gaseous products thus formed aid in extinguishing the power arc.

It should be kept in mind that the maximum are expected is one related to normal loads and the switch is not intended to interrupt anything greater than normal load, a circuit breaker or interrupter being provided in series with the disconnect switch for opening under other than normal load.

Thus, it will be seen that the arcing contacts make first on closing and break or open last on the opening operation of the switch. This sequence is important to prevent damage to the main contacts.

The actual structure of the novel disconnect switch is shown particularly in FIGS. 11, 12, 13, 14 and 15. As seen in these figures, the shaft 160 which carries the worm 161 (see particularly FIGS. 11 and 12) drives the worm gear 142. Worm gear 142 in turn drives the shaft 115. The bell crank 114 is rotatably mounted so that it may rotate freely with respect to the shaft 115. The bell crank 114 is connected at the pin 113 to the operating link 112-122 which in turn is connected to the disc shaft operating crank 111. The spring carrier 130 is arranged to have two springs which operate on the toggle pin 118 as previously described, the two springs 131 being shown in FIGS. 12 and 15. The crank 140 which operates the spring carrier as previously described is shown as a pair of parallel cranks both keyed to the shaft 115 and rotatable therewith so that they will operate the pins 144 on each side of the spring carrier 130. The shaft 115 is supported in appropriate bearings on appropriate standard 130a on the bottom frame member 210 as previously described. The motion of the bell crank lever 114 must be communicated to the poles 270, 271 on each side (FIGS. 11 and 12). For this purpose, a jack shaft 272 is carried by the bell crank 114 connected to the crank 273 on jack shaft 274 for pole 65 270 and crank 275 on jack shaft 276 for pole 271. Each of the shafts 274 extend coaxial with the operating shaft 115 of the center pole. Each of the shafts 274 and 276 is provided with a crank 278, 279 (see also FIGS. 11 and 12) which will operate corresponding links 112a-122a, l12b-122b for the respective poles 270 and 271. Thus, the operation of the single central pole will effect simultaneous and similar operation of the poles on each side by the utilization of operating members peculiar only to the central pole (see also FIGS. 13, 14 and 15).

In FIG. 14, alternate forms of connection of the upper back connection stud 101 are shown. The entry from the bus may be through the top of the housing, as shown by the connector 101 for each of the poles or alternatively, the entry-may be through the back of the housing as shown by the connectors 101a, 101b and 101C, one for each of the poles.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A double break disconnect switch having a pair of movable contacts and a pair of complementary contacts;

a rotatable disc of insulating material; the said movable contacts being slidably mounted within said disc and extending radially thereof; the

said movable contacts extending substantially opposite each other on opposite sides of the center of said disc; I

the said complementary contacts being located also on substantially opposite sides of the center of said disc;

means for rotating said disc to a position in which said movable contacts register with said complementary contacts;

said means being operable, when said contacts so register, for moving said movable contacts into engagement with said complementary contacts;

said means being further operable in a reverse direction for opening said switch by first withdrawing said movable contacts from engagement with said complementary contacts and thereafter rotating said disc until each movable contact is substantially equidistant from both complementary contacts.

2. The double break disconnect switch of claim 1 in which each movable contact, when said switch is open, is fully recessed within said disc.

3. The double break disconnect switch of claim 2 having:

biasing means carried by said disc and individual to and engaged with each movable contact driving each movable contact toward the center of said disc and away from said complementary contacts;

said means for rotating said disc also operating s aid movable contacts when they are in registry with the complementary contacts toward engagement with the complementary contacts against said biasing means.

4. The double break disconnect switch of claim 3 in which:

said means for rotating said disc comprises a shaft located centrally of said disc;

a double ended crank on said shaft;

a connection between each end of said crank and one of said movable contacts;

rotation of said crank in one direction when the switch is closed being operable through said connections to move said movable contacts away from said complementary contacts;

said disc having a pair of opposite crank receiving surfaces;

further rotation of said crankin said one direction thereafter rotating said disc and said movable contacts to a position wherein each movable contact is substantially equidistant from the complementary contacts.

5. The double break disconnect switch of claim 3 wherein a housing is provided for each of said complementary contacts;

each housing extending on either side of each complementary contact and having a surface adjacent the disc in a curved parallel relation thereto.

6. The double break disconnect switch of claim 3 wherein:

arc extinguishing means are provided comprising:

a movable arcing contact in electrical parallel relation with each movable contact;

a stationary arcing contact in electrical parallel with each complementary contact;

an arc extinguisher connected to the housing of each complementary contact and extending in a curved path parallel to the surface of said disc;

each movable arcing contact being carried by said disc and moving, when said disc rotates, in said are extinguisher; each movable arcing contact, on rotation of said disc toward closed contact position, engaging its stationary arcing contact before the first mentioned contacts engage;

and on rotation of said discs toward open contact position disengaging its stationary arcing contact after the first mentioned contacts disengage. 7. The double break disconnect switch of claim 4 in which overcenter toggle linkage means are provided for operating said shaft and crank from a contact engaged position of the disc to a contact disengaged position and back again to the contact engaged position;

a second driving crank on said shaft, a link connected to and driving said camk;

said link being connected to said overcenter toggle linkage and springmeans connected to said toggle linkage biasing said toggle linkage to break on either side of center. 

1. A double break disconnect switch having a pair of movable contacts and a pair of complementary contacts; a rotatable disc of insulating material; the said movable contacts being slidably mounted within said disc and extending radially thereof; the said movable contacts extending substantially opposite each other on opposite sides of the center of said disc; the said complementary contacts being located also on substantially opposite sides of the center of said disc; means for rotating said disc to a position in which said movable contacts register with said complementary contacts; said means being operable, when said contacts so register, for moving said movable contacts into engagement with said complementary contacts; said means being further operable in a reverse direction for opening said switch by first withdrawing said movable contacts from engagement with said complementary contacts and thereafter rotating said disc until each movable contact is substantially equidistant from both complementary contacts.
 2. The double break disconnect switch of claim 1 in which each movable contact, when said switch is open, is fully recessed within said disc.
 3. The double break disconnect switch of claim 2 having: biasing means carried by said disc and individual to and engaged with each movable contact driving each movable contAct toward the center of said disc and away from said complementary contacts; said means for rotating said disc also operating said movable contacts when they are in registry with the complementary contacts toward engagement with the complementary contacts against said biasing means.
 4. The double break disconnect switch of claim 3 in which: said means for rotating said disc comprises a shaft located centrally of said disc; a double ended crank on said shaft; a connection between each end of said crank and one of said movable contacts; rotation of said crank in one direction when the switch is closed being operable through said connections to move said movable contacts away from said complementary contacts; said disc having a pair of opposite crank receiving surfaces; further rotation of said crank in said one direction thereafter rotating said disc and said movable contacts to a position wherein each movable contact is substantially equidistant from the complementary contacts.
 5. The double break disconnect switch of claim 3 wherein a housing is provided for each of said complementary contacts; each housing extending on either side of each complementary contact and having a surface adjacent the disc in a curved parallel relation thereto.
 6. The double break disconnect switch of claim 3 wherein: arc extinguishing means are provided comprising: a movable arcing contact in electrical parallel relation with each movable contact; a stationary arcing contact in electrical parallel with each complementary contact; an arc extinguisher connected to the housing of each complementary contact and extending in a curved path parallel to the surface of said disc; each movable arcing contact being carried by said disc and moving, when said disc rotates, in said arc extinguisher; each movable arcing contact, on rotation of said disc toward closed contact position, engaging its stationary arcing contact before the first mentioned contacts engage; and on rotation of said discs toward open contact position disengaging its stationary arcing contact after the first mentioned contacts disengage.
 7. The double break disconnect switch of claim 4 in which overcenter toggle linkage means are provided for operating said shaft and crank from a contact engaged position of the disc to a contact disengaged position and back again to the contact engaged position; a second driving crank on said shaft, a link connected to and driving said carnk; said link being connected to said overcenter toggle linkage and spring means connected to said toggle linkage biasing said toggle linkage to break on either side of center. 